1. Field
The present disclosure relates to an uninterruptible power supply (UPS), more particularly, to an isolation control high speed transfer switch for UPS and a power supply system using the same, while independently operating with UPS, which is capable of more stably switching a power supply path from a normal power line to a bypass line without a hit (momentary power failure), even when there is a possibility of generating the hit since the power supplying function through the normal power line is impossible due to the malfunction of the UPS and the control function is also impossible.
2. Discussion on the Related Technology
In most cases, UPS is designed to supply a stable power to a load by outputting a uniform voltage and frequency even when the common power source has a power failure without a notice or an input power is non-uniform,
FIG. 1 is a configuration diagram showing the configuration of an uninterruptible power supply (UPS) of the related art. In a normal mode, in case an alternating current AC power is inputted to UPS through a transfer switch CB1, the inputted alternating current AC power is transformed into a direct current DC power in a rectifier 1. The transformed direct current DC power is supplied to an inverter 2 and, at the same time, the battery 3 is charged. The inverter 2 transforms again the output power of the rectifier 1 into the alternating current to provide to a load. At this time, the state of an output breaker CB3 becomes turn-on, while the state of a transfer switch STS, CB4 of a bypass module 4 becomes turn-off. In case the input power is blocked-off due to an electricity failure, DC power that is charged in the battery 3 is transformed into AC power to supply to a load. Here, a path where the input power or DC power of the battery 3 is supplied through the inverter 2 is called as normal power line.
However, when the malfunction of the inside of UPS or the exterior momentary short-accident is generated in the state where the input power is normally inputted, the electric power through the normal power line, sometimes, can not be supplied. In this case, the control means (not shown) of UPS blocks off the normal power line by turning off the output breaker CB3, and switches the power supply path from the normal power line to the bypass line by turning on the transfer switch STS, CB4 of the bypass module 4. Thus, the input power is immediately supplied to the load through the bypass line. At this time, ON signal is applied to the transfer switch CB4 of the bypass module 4 and, simultaneously, to the static transfer switch STS, thereafter, the transfer switch CB4 is turned on, immediately after the static transfer switch STS is turned on.
Hereinafter, methods used in UPS of the related art for switching to the bypass line will be described. First, while the fuse which is located in output terminal of the inverter 2 is melted and cut, UPS blocks off the electric power which is supplied through UPS. Then, UPS detects the melting signal, and switches the power output line to the bypass line,
Second, in the drain of the inverter 2, UPS detects whether the output power becomes “0” or not, and blocks off the gate of Insulated Gate Bipolar Transistor (IGBT) which is a power conversion device of the inverter, and, at the same time, switches the power supply path to the bypass line.
Third, UPS detects the output signal of the fuse which is located in the output terminal of inverter, and switches the power supply path to the bypass line according to the signal. Fourth, none of the above-described three methods is used, or the second and the third method can be mingled to be used.
In the meantime, in most cases, the 98% among the reason of the power failure generated in the communications industrial site is resulted from the malfunction of the inside of UPS, while the 82% among them is caused by the short circuit of a rectifier and an inverter power conversion device and by the damage of transistor due to a fire. In case a bulk current is flowed into the inside due to the malfunction of the inside of UPS, the damage by a fire is generated in the whole control device, with a burning. Furthermore, in case the switching to the bypass line is delayed, the output breaker of UPS is damaged by a fire due to an overheat such that the malfunction may be generated and a big accident may be caused.
Therefore, in case of the above-described first method, when the function of the controller (not shown) is deprived due to the transient situation in which the fuse is melted, frequently, the switching is not normally performed. Additionally, the power conversion device has the problem that the operation is not performed in the open state which is not short-accident state, that is, the output stop state.
In case of the second method, it should pass through the process of trouble detection→IGBT gate block off→output stop→output power detection→transmitting to CPU→malfunction determination→by-pass command→switching. In this case, no matter what fast device is used, the switching time is detected over 208˜290 ms by the actual measurement. This exceeds 4 ms which is the basic specification of UPS, then, the state of the load already becomes the stationary state. Further, in case the function of a controller is deprived like the first method, it can be an uncontrollable state.
In case of third and fourth method, the switching time can be extended over 8˜24 ms like the second method. Furthermore, in case of losing the control function, the operator has to supply power mechanically. Therefore, the switching time is required over 190˜600 ms such that it can utterly be the stationary state.
Furthermore, in the interlock machine having a structure where the transfer switch CB4 is turned on when the output breaker CB3 is blocked while the mechanical transfer switch and the output breaker CB3 of the bypass module 4 (not shown) are formed as the interlock device, in case the failure of UPS control function happens, as shown in (c) of FIG. 2, the switching time can be required over 670˜690 ms.
FIG. 2 shows graphs showing the change of the state of UPS output power in case the malfunction of UPS with the malfunction of the control is generated when UPS is operated according to the related second and the third method.
Furthermore, as to the switching of the power supply path, in case the power supply path is switched to the bypass line, the output breaker CB3 has to be turned off That is, the control means (not shown) of UPS 10 outputs OFF signal for the output breaker CB3 before turning on the transfer switch STS, CB4 of the bypass module. On the other hand, the signal of OFF for the output breaker CB3 was normally outputted, however, the output breaker CB3, actually, may not be normally turned off For example, in case the contact point of the output breaker CB3 is melted and sticked, the output breaker CB3 is not normally turned off even in case the OFF signal is generated. In this case, the output power of UPS as well as the power through the bypass line is supplied together to the load to cause a bigger trouble.
However, the UPS immediately turns on the static transfer switch STS while not confirming the normal condition of the output breaker CB3, it has the problem of generating other troubles.
The foregoing discussion in the background section is to provide general background information, and does not constitute an admission of prior art.